Breeding shortcut brightens future for valued tree

- off the danger list

The obeche tree, the stricken green giant of West Africa, is to rise again across six countries of the region. In the long term, it may also be introduced to Asia and Latin America to help in the reversal of the relentless current degradation of tropical forests.

The success story of UK and Nigerian scientists whose collaboration has rescued the obeche tree (Triplochiton scleroxylon), a source of highly marketable timber, represents merely one small advance in a vast sphere beset by monumental disasters. Rapid population growth, land hunger and ill-conceived industrialization are blamed for the destruction of an estimated 6.5 million ha of forestland a year in the developing regions alone, leading to irreversible ecological damage. If the current trends are allowed to continue, many fear that the mighty tropical forests as we know them may disappear within three decades.

The West African research programme running counter to these trends, operated by the Institute of Terrestrial Ecology near Edinburgh and the Forestry Research Institute of Nigeria in Ibadan, began 20 years ago. It has led to a whole new range of propagation techniques applicable not just to the obeche but to most other tropical trees also. New plantations of obeche are now taking root in Nigeria. "Now that these techniques are tried," comments Dr. Roger Leakey, a senior scientific officer engaged in the project, "ifs just a matter of expanding the work to equally endangered species in other parts of the world."

Until recently, the obeche tree was one of the most prized species on the danger list. It takes up to 40 years to form a worthwhile tree that may ultimately reach 61 m. Its timber is suitable for furniture, for joinery as well as veneers. It can also be pulped. Over the years, the best trees were selectively cut down. The survivors available for natural regeneration consequently included the least desirable specimens. The decline of the obeche was dramatically illustrated by its drop within a short space of time from 60 percent of Nigeria's total timber exports to nil. The tree's erratic seed production made proper planting programmes impossible. Its seed-bearing fruits are formed unpredictably and few of them ever reach maturity because of pests and diseases.

So the scientists have had to learn to climb 72 selected trees to collect as well as dry and store what seeds they did find. The rescued seeds were used in a programme of multifaceted research exploring the differences between the trees in different locations. Unlike the progeny of wheat, those of many trees are highly variable, lending themselves to rapid programmes of improvement.

The scientists also developed methods of obtaining large numbers of plantlets by vegetative propagation from cuttings or through the grafting of shoots to rootstocks. Already, some of them have yielded viable seeds within four years - compared to the usual 40 years in the field.

Thus the project has made the versatile obeche a likely choice for upgrading threatened tropical forests. At present, it occurs in a narrow belt of humid tropical forest extending about 4 000 km and traversing six or more West African countries. It is also found in small groups in some of the drier savannas, possibly the remnants of larger stands that were cleared by semimigrant cultivators.

The UK Overseas Development Administration has announced a fresh research grant for the project. The next task, explains a spokesman there, is the development of methods to predict the form of mature trees from the characteristics of seedlings.

"In the course of time," he goes on, "we hope that the obeche can be introduced into parts of tropical Asia and America. A forthcoming screening trial of 20 other hardwood species may also indicate alternative sources of timber."